Designing Ce single-atom-sites coupled with CeO2 nanoparticles for oxygen reduction enhancement

Non-precious metal Fe–N–C materials are considered one of the promising substitutes for the Pt/C catalyst toward the oxygen reduction reaction (ORR). However, they still suffer from rapid stability reduction caused by the severe Fenton reaction in the ORR process. Here we report a supramolecular-gel-pyrolysis (SGP) method to design a non-noble CeO2/Ce-N–C composite with a hierarchically porous carbon sheet-network structure, serving as an efficient Ce single-atom-site (Ce-N4O4) catalyst for the ORR in a zinc–air battery (ZAB). The prepared catalyst displays comparable ORR catalytic activity and stability to those of Pt/C in an alkaline electrolyte. The corresponding ZAB tests also show a higher energy density and better long-term cycling durability. Theoretical calculations indicate that the enhanced ORR activity may be attributed to the fact that the presence of oxygen vacancies and the Ce-N4O4|CeO2 coupling sites can largely favor the chemical adsorption and activation of O2. This work provides a new avenue for exploring rare-earth metal single-atom ORR electrocatalysts with coupled ORR catalytic sites.